1. Field of the Invention
The present invention relates generally to moisture-absorbent compositions and molded items, and more particularly to those having an indicator function of showing colors changing in accordance with the rate of moisture absorption.
2. Description of the Related Art
Oxidation, corrosion, liquefaction, etc. due to moisture absorption results in degradation in quality of foods, medicines, electronic parts, precision instruments, daily necessaries, etc. To prevent such oxidation, corrosion, etc., these items are contained in water-vaporproof metallic cans or glass bottles, or wrapped with films having a low water vapor permeability and made of polyethylene, extended polypropylene, polyvinylidene chloride, aluminum foil, etc. In addition, desiccants such as silica gel, calcium chloride, quick lime, or zeolite are sealed in such containers or packages. When used, these desiccants are put, in the form of particles or powder, in paper bags, cloth bags, or containers. As a result, the inherent excellent properties of the desiccants are not fully exhibited. If the container of the desiccant is damaged or broken, the desiccant may adhere, or may be kneaded in, the item in the container. Furthermore, the use of a deliquescent desiccant may lead to a liquefaction phenomenon. In addition, it is difficult to examine the moisture absorption effect of the desiccant with the naked eye, and the gradual change of moisture absorption effect cannot be understood.
Published Unexamined Japanese Patent Application No. 61-227818 proposes a technique of preventing a leak of liquid due to moisture absorption liquefaction, wherein micro-porous thermoplastic resin sheet is employed as a packaging material for desiccants. There is also proposed a technique wherein non-woven cloth and composite desiccants are alternately laminated. These techniques, however, have problems such as high costs, trouble in using the desiccant, careless swallow of the desiccant, etc.